The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In general, an oxygen sensor is mounted in an exhaust manifold of a vehicle and measures the concentration of oxygen in exhaust gases, and the oxygen sensor may use zirconia generating electromotive force when oxygen quantity on both zirconia surfaces of the oxygen sensor becomes different. That is, the oxygen sensor may use a principle of measuring the concentration of oxygen according to the degree of electromotive force generated by zirconia positioned between the exhaust gas and air in the atmosphere.
For example, when an air-fuel ratio in the exhaust gas is rich (i.e., fuel is rich and oxygen is lean), the concentration of oxygen in the exhaust gas is lower than the concentration of oxygen in the atmosphere and thus electromotive force is generated by the oxygen sensor. By contrast, when the air-fuel ratio in the exhaust gas is lean (namely, fuel is lean and oxygen is rich), the concentration of oxygen in the exhaust gas does not differ from the concentration of oxygen in the atmosphere and thus electromotive force is not generated by the oxygen sensor.
Fuel injection control techniques according to the related art adjust an air-fuel ratio (a ratio between the quantity of air and the quantity of fuel) of a mixture injected into a cylinder in an engine of a vehicle on the basis of the concentration of oxygen in exhaust gases. However, we have discovered that the fuel injection control technologies do not consider a torque deviation between individual cylinders of the engine, and thus it causes cylinder imbalance.
As a result, the fuel efficiency of the vehicle may be reduced and the quantity of exhaust gases may be increased. In addition, the durability of the engine may be undermined.